Tropical Depression FOUR

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TROPICAL DEPRESSION FOUR DISCUSSION NUMBER 5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL042006
500 PM EDT TUE AUG 22 2006
DESPITE SOME INCREASE OF CONVECTION NEAR THE CENTER THIS
AFTERNOON...THERE IS LIMITED BANDING AND DVORAK INTENSITY ESTIMATES
FROM TAFB AND SAB REMAIN AT 30 KT. CONSEQUENTLY THE SYSTEM WILL NOT
BE UPGRADED AT THIS TIME. HOWEVER...WITH CONVECTION ON THE INCREASE
THE CLASSIFICATIONS SHOULD SUPPORT TROPICAL STORM STRENGTH VERY
SOON. WHILE THE OUTFLOW PATTERN HAS BEEN IMPROVING TODAY AND THE
SHEAR IS FAIRLY LOW...THE CYCLONE WILL BE MOVING OVER SLIGHTLY
COOLER WATERS AND A MORE STABLE BOUNDARY LAYER FLOW...SO I AM
ANTICIPATING ONLY SLOW DEVELOPMENT OVER THE NEXT COUPLE OF DAYS.
AFTER THAT...WATERS WARM BUT SOME OF THE GLOBAL MODELS SUGGEST AN
INCREASE IN SOUTHERLY SHEAR ASSOCIATED WITH AN UPPER-LEVEL LOW IN
THE CENTRAL ATLANTIC. BOTH THE SHIPS AND GFDL MODELS HAVE BACKED
OFF SLIGHTLY WITH THEIR INTENSITY FORECASTS AND THE OFFICIAL
FORECAST IS ALSO NUDGED DOWN.
THE INITIAL MOTION IS 300/16...OR ABOUT 15 DEGREES TO THE RIGHT OF
THIS TIME YESTERDAY. RECENT MICROWAVE PASSES SUGGEST A BETTER
CO-LOCATION OF THE MID AND LOW-LEVEL CENTERS. THERE HAS BEEN
SIGNIFICANT CONVERGENCE IN HOW THE GLOBAL MODELS HANDLE THE
DEPRESSION...WITH THE 12Z RUNS OF THE UKMET AND ECMWF NOW
MAINTAINING THE SYSTEM AND SHIFTING THEIR TRACKS TO THE RIGHT.
THEY ARE NOW IN GOOD AGREEMENT WITH THE GFS AND ALSO WITH THE GFDL
THROUGH ABOUT 72 HOURS. THERE HAS BEEN LITTLE CHANGE TO THE
SYNOPTIC SITUATION...WITH ALL THE GUIDANCE INDICATING AN EASTWARD
SHIFT OF THE SUBTROPICAL RIDGE AND TROUGHING DEVELOPING OVER THE
CENTRAL ATLANTIC. THE OFFICIAL FORECAST HAS BEEN SHIFTED SLIGHTLY
TO THE RIGHT OF THE PREVIOUS TRACK AND IS IN BEST AGREEMENT WITH
THE GFS AND ECMWF.
FORECAST POSITIONS AND MAX WINDS
INITIAL 22/2100Z 14.5N 27.5W 30 KT
12HR VT 23/0600Z 15.7N 29.7W 35 KT
24HR VT 23/1800Z 17.2N 32.4W 40 KT
36HR VT 24/0600Z 18.8N 35.2W 40 KT
48HR VT 24/1800Z 20.1N 38.0W 45 KT
72HR VT 25/1800Z 23.0N 44.0W 50 KT
96HR VT 26/1800Z 27.0N 49.0W 55 KT
120HR VT 27/1800Z 30.0N 53.0W 60 KT
$$
FORECASTER FRANKLIN
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